That's the ex Reading's freight mainline to Reading. North of Falls Bridge Philly it's definitely Norfolk Southern. Between Falls Bridge and Columbia Railroad Bridge some of it may be CSX, since CSX crosses and double crosses the river at both those spots, each of which are good photo spots.
There's not much public transit between Conshohocken and Manyunk other than the R6 train. If you can handle the walk or bike ride, I'd suggest walk between then Manayunk, Miquon or Spring Mill stations. The canal towpath and ex Pennsy right of way are bike-hike trails, and I think Flat Rock dam is a good place to shoot from the path, you can get a decent look at the canal locks, dam, river and railroad, although maybe not all in one shot.
There's absolutely no public transit on the Norfolk Southern railroad's side of the river, and only a few spots with road access, but getting off the train in Manayunk you could walk across the Belmont Ave-Green La bridge, then make a right turn after going under the railroad and expressway, that street climbs up the hill and there are some nice shots available, as well as my high school buddy's house, whose back porch has a good view. Naturally he pretended he wasn't a railfan when he dickered with the guy from whom he bought the house.
If you're driving, the river road, right turn from the interstate 76 west Gladwynne exit, has lots of spots right on the railroad, and a township park with small parking lot just a bit north of Flat Rock dam and tunnel.
City Ave bridge has good views, and a pedestrian sidewalk on at least one, maybe both of its spans, but I'm not sure how one gets to it from the West Philly-Bala Cynwyd side without getting run over.